Method of die casting the tread design in a matrix blank



Jan. 24, 1956 J. .1. FANNEN 2,731,689

METHOD OF DIE CASTING THE TREAD .FAg. 7 6 8 John JFaz-anen Jan. 24, 1956 FANNEN 2,731,639

METHOD OF CASTING THE TREAD DESIG N A MATRIX BLANK Original Filed April 18, 1949 2 Sheets-Sheet 2 WW 0 i o \o 1/ a l MAW o o o VENTOR John J nnen av 0 Wi/ ATTORNEYS United States Patent 3. 2,731,689 METHOD OF DIE CASTING THE TREAT) DESIGN IN A MATREX BLANK John J. Fannen, Lotti, Caiif., assigner to Super Mold Corporation of California, Ledi, Calif, a corporation of California Continuation of appiication Serial No. 88,178, April 18, 1949. This application December 16, 1952, Serial No. 326,219.

1 Claim. (Cl. 22-268) This invention relates to the tire making or retreading industry, and particularly to the matrix in which a tire carcass is placed for the vulcanizing of the tread thereon.

This application is a continuation of abandoned application filed April 18, 1949, Serial No. 88,178.

The treads of pneumatic vehicle tires, for non-skid purposes, are formed with circumferential grooves of various configurations which, in the matrix, are, of course, in the form of relatively narrow projecting fins or tongues, and the shape of the tongues governs the design of the finished tread.

It is customary, when making the matrix, to machine the inner tread engaging face of the matrix blank while said face is unbroken, and to then apply the tread-groove or design forming fins.

This is done by placing a fin-grooved die against the machined inner face of the blank, and forcing molten metal into the die through holes drilled from exteriorly of the matrix blank to said inner face, as shown, for instance in Patent No. 1,989,438.

At present, the metal in these holes-which, of course, only occur at spaced intervals--forms the only bond or tie with the fin forming metal for the length of the die, since there is no actual fusion of the metal of the fins with that of the matrix blank. As a result, the formed fins, which are somewhat narrow and hence relatively weak, tend to break ofii' rather readily, tying up tire production while repairs are made to the matrix.

It is, therefore, the major object of this invention to eliminate the above defect by providing a method of casting the fins into the matrix blank in such a manner that a continuous and much stronger tie with the blank is bad than is now obtained, and Without the use of any more drilled holes in the blank than are now necessary, and without any change being made in the die.

The manner in which the improved method is carried out is illustrated in the accompanying drawings in which:

Figure 1 is a fragmentary radial sectional elevation of a matrix blank seated in a die casting apparatus and with the tread-design die in place against said blank, but before pouring the tread-design forming metal.

Figure 2 is a fragmentary radial section of the matrix after the tread-design fins have been poured.

Figure 3 is a fragmentary elevation of the matrix, looking at the tire engaging face thereof and showing the tread-design fins as formed along a portion of the matrix.

Figure 4 is a fragmentary sectional plan of the matrix on line 4-4 of Fig. 3.

Referring now more particularly to the characters of reference on the drawings, the matrix blank to which the tread-design fins are to be applied is indicated by the numeral 1, and is of generally conventional form, having an initially smooth-machined inner working or tire tread engaging face 2.

This blank is adapted to be mounted with its axis vertical, in a die casting machine such as that shown in the aforementioned Patent No. 1,989,438, or in Patent No. 2,478,657. Such machine includes an upstanding heated wall member 3 against which a portion at a time of the outer wall 4 of the matrix blank 1 seats in sealing relation, the member 3 having a molten-metal feed passage 2,731,689 Patented Jan. 24, 1956 2 5 therethrough to communicate with the outer wall 4 of said matrix blank 1.

A segmental die block 6, having rows of tread-design depressions or grooves 7 therein, is shaped to be disposed against and matchingly engage the face 2 of the matrix blank and to be held in sealing relation with the blank while the metal is poured; the die being moved ahead step by step as fully described in said patents.

In order that metal forced through passage 5 may enter the die, holes 8 are drilled through the matrix blank at intervals about the same to communicate with the passage 5 and with the die grooves or recesses 7.

Previously, as shown in the patents, these holes led directly to the working face 2 of the matrix blank 1 and registered with the die grooves 7, so that the sole tie between the metal in said grooveswhich extend the full length of the die-and the working face of the blank 1 was at the holes 8, which are relatively widely spaced.

With the improved method, however, relatively deep annular groove 9 are first machined in the matrix blank, one forand registering with-each row of die grooves 7. The annular grooves 9 are as wide as the overall width of the recessed pattern which, in the present instance, is Zigzag as clearly shown in Fig. 3. The holes 8 lead to the bottom of grooves 9, as shown.

Thus, when the die cast metal is poured, the fins 10 are integral with a continuous base strip 11 in grooves 9, and with the metal 12 remaining in holes 8. As a matter of fact, metal 12 is no longer relied on or necessary as a tie for the fin structure, since the latter, when completely poured about the matrix blank and thus forming an unbroken unit, can never come out as will be obvious.

It will, of course, be understood that a removable block or gate is used at the end of the die to close each groove 9 as the metal is poured through holes 8 into the groove and die, so as to prevent metal fiowing into the groove beyond the die.

From the foregoing description it will be readily seen that there has been produced such a method as substantially fulfills the objects of the invention, as recited herein.

While this specification sets forth the present and preferred details of the method, still in practice such deviations from such detail may be resorted to as do not form a departure from the spirit of the invention as claimed.

Having thus described the invention, the following is claimed as new and useful and upon which Letters Patent are desired:

In the tire treading industry, the method of forming and anchoring a tread design fin on the initially plain working face of a tire-tread matrix blank with the aid of a segmental die block grooved to provide a tread-fin pattern, comprising first cutting a continuous annular groove in said face of the matrix blank, placing the die block against the face of the matrix blank in successive steps for the full circumferential extent of said matrix blank so that with each step the grooving in the die block communicates with a corresponding portion of the groove in the matrix blank, and forcing molten tread-design metal into the die block grooving for the length thereof and into the corresponding portion of the annular groove to completely fill such grooving and groove portion, and repeating such metal forcing operation with each successive step positioning of the die block.

References Cited in the file of this patent UNITED STATES PATENTS 1,590,392 Peters June 29, 1926 1,989,438 Woock Jan. 29, 1935 2,201,024 Brown May 14, 1940 2,467,218 Mittermaier Apr. 12, 1949 2,478,657 Glynn Aug. 9, 1949 2,593,547 Duerksen Apr. 22, 1952 

